#include <iostream>
#include <algorithm>
using namespace std;

int main(int argc, char const *argv[]){
    char data[201], temp;
    int count = 0;
    while(cin >> temp)
        data[count++] = temp;
    sort(data, data+count);
    for (int i = 0; i < count; i++)
        cout << data[i];
    cout << endl;
    return 0;
}